It is known, as for example for U.S. Pat. No. 3,471,134 or German patent publication No. 2,615,431, to support a workpiece in a furnace on internally cooled support tubes. Two sets of such tubes are frequently provided to form a walking-beam conveyor.
In order to prevent the supports from heating excessively, they are formed entirely as tubes through which a fluid coolant such as air or steam is circulated. Normally this circulation takes place from one end to the other of the horizontal tubes. These tubes are in turn supported on vertical posts that must also be cooled. Thus these posts also are formed as tubes. Since considerable thermal expansion takes place in these arrangements it is normally necessary to close off the lower ends of the vertical support tubes and support them on carriages or the like that allow them to travel limitedly in the longitudinal direction in which the horizontal tubes expand.
Cooling of these vertical support tubes as well as the horizontal tubes is effected by means of a small-diameter diversion pipe that is provided at the joint between the upper end of each of the vertical tubes and the respective horizontal tube. Such a diversion pipe has an upper leg opening in the upstream direction, that is against the direction of flow through the horizontal tube, and a lower leg open downwardly into the center of the respective vertical tube. This lower leg is received with all-around clearance in the vertical tube. Thus some of the fluid coolant moving along the horizontal tube will enter the intake end of the diversion tube and will be injected from the output end thereof into the vertical tube. This diverted coolant cools the vertical tube and then rises in the annular space around the diversion pipe to rejoin the stream flowing along the horizontal tube. Such an arrangement ensures thar the same coolant stream will flow at least partially through the vertical support legs so as to prevent them from being excessively heated and, hence, weakened.
A disadvantage of this type of arrangement is that considerable turbulence is created at the joint where the upper end of each of the vertical tubes is connected to the respective horizontal tube. This turbulence is caused in part by drawing-off some of the flow from the horizontal tube, and in part by readmitting fluid into the horizontal tube. As a result of this turbulence the flow rate through the system and, with it, the overall cooling efficiency are reduced considerably.